Method of dispersing keratin protein with ammonium thiocyanate and the composition resulting therefrom



I of such keratins, either in the Patented July 13, 1943 METHOD OF msrcasmo NIUM 'rmocram'rn TEIN WITH AMIH AND THE COMPOSITION THEREFROM Chase B. Jones, Waltham,

Richmond, Calif., America as represented by the Secre- Mecham, States of tary of Agriculture KERATIN PRO- RESULTING Mass., and Dale K. assignors to United No Drawing. Original application November "I,

1944, Serial No. 562,326.

May 8, 1947, Serial No. 746,850

plication Divided and this ap- 4 Claims. "(01. 106-15 5) (Granted under the act of March amended April 30, 1928; 37.0 0.

This application is made under the act oi March 3, 1883, as amended by the act of April 30, 1928, and the invention herein described, if patented, may bemanufactured and used'by or for the Government of the United States of v America for governmental purposes without the payment to us of any royalty thereon.

This application is a division of our copendlng application for'patent, Serial No. 562,326, filed November '7, 1944.

This invention relates to a method of dispersing keratin proteins obtained from a keratin material such as feathers, hoofs, horns, wool, and so forth, and has among its objects the use dispersed or recovered forms, in the preparation of artificial fibers, films, plastics and the like. I

Keratins, like the more soluble proteins, can be readily dispersed by hydrolysis in strong acids or alkalis, but the keratin thus dispersed cannot be recovered except as simple degradation products, such as amino acids or complex degradation products, such as peptides, peptones, and prov teoses, the properties of which diiler radically from those of the original keratin.

Keratins can also be dispersed in alkaline solutions of metallic sulphides and I such sulphides are commonly used in cosmetic depilatories and in the removal of hair from hides in the tanning industry.

Keratin's have also been dispersed at neutral reactions but in these cases heat and high temperatures were employed to the point of charring, which produced drastic degradation of the proteins.

Also, keratins may be dispersed in strong alkaline solutions by treatment with reducing agents,

and the recovered protein is more similar to theoriginal protein in regard to solubility, molecular size, and so forth, than are the peptides, proteoses, etc., referred to previously. However, the *presence of the strong alkali is undesirable because it presents an opportunity for the hydrolysis of the keratin, destruction of the cystine constituent of the keratin (keratins being unique among proteins in that they contain exceptionally large amounts of cystine), and destruction of the hydroxy amino acid residues of the keratin.

According to our invention, keratin materials are dispersed under mild conditions, that is, in

3, 1883, as G. 157) neutral or practically neutral reaction, and at relatively low temperatures. These conditions produce less degradation of the original keratin than occurred in the prior art and the dispersed keratin may be recovered in a form substantially similar to that of the original keratin in regard to its composition, isoelectric point, solubility, and other properties.

The method involved in this invention is based partly on the reductionof'the disulphide bonds within the keratin molecule by treating it with sulfur-containing, reductive disulphide-splitting agents such as monoethylene thioglycol (thioglycol), thioglycolic acid (present as the thioglycolate in neutral solution), and sodium bisulphite.

The presence of alkali is obviated by the use of any of a number of protein-denaturing or protein-dispersing agents, such as urea, guanidine hydrochloride, ammonium thiocyanate, formamide, acetamide, thiourea, sodium salicylate,

urethane, phenol, lithium iodide, and surface-- active agents, such as synthetic detergents composed of sodium alkyl aryl sulfonates, sodium alkyl sulfates, and so forth, and dispersion of the keratin is thus effected at neutral or practically Example I 1.4 parts of monothioethylene glycol and 27.2 parts of guanidine hydrochloride are dissolved in water. Sodium hydroxide solution and water are then added as required to obtain 35 parts of solution at about pH 6.9. 2.5 parts of cattle hoof filings are treated with this neutralized solution in a water bath at about 40 C. about for 18 hours. The mixture is stirred at convenient intervals. During this period about 74% of the hoof keratin is dispersed in the solution. After removal of the undlspersed hoof by filtration, the dispersed 3 keratin may be precipitated either by dilution with several volumes of water, by salting out with MgSO4, (NHO 2804, etc., by acidification, or by dialysis. If desired, the guanidine may be removed from the dispersion by dialysis and may 5 be recovered from the dialysate by precipitation as the nitrate or by other suitable means.

Example I! 1.1 parts, of NaHSOa and 21 parts of urea are dissolved in water. Sodium hydroxide solution and water are added as required to obtain 85 parts of solution at about pH 7.1. 2.5 parts of wool are treated with this solution in a water bath at about 40 C. about for 18 hours, during which period the mixture is stirred at frequent intervals. 52% of the original weight of the wool is dispersed by this treatment. The dispersed wool may be precipitated and recovered from the solution eitherby dialysis, by salting out with M3804, 2o

(NH4) 2504, etc.. or by careful addition of a suitable amount of acid or alkali.

Example III 40 parts of a synthetic detergent composed of sodium alkyl aryl sulphonates, and 4 parts of NaHSOa are dissolved in water. Sodium hydroxide solution and water are added as required to obtain 400 parts of solution at about pH 6.6.

This solution is heated to boiling and 64 parts so of chicken feathers are added. The solution is kept boiling gently for about minutes with frequent stirring. During this period considerable dispersion of the feathers occurs and the 1 undispersed portion becomes very soft and loses 5 its original shape. 200 parts of boiling water are now added and the solution is boiled and stirred for about another 30 minutes. The undispersed residue is removed by suitable filtra- The washings and filtrate may be combined and evaporated to dryness to obtain-70 parts of a water-soluble product that has been found use-/ ful for the preparation of artificial fibers. This material contains 85% to 8.6% nitrogen on a 45 dry basis.

Example IV 50 parts of a synt'etic detergent, composed of sodium alkyl NaHSOa are dissolved in 940 parts of water; A saturated solution of sodium hydroxide is added until the pH of the solution is about 6.0. The solution is heated to boiling and 80 parts of chicken feathers are added The solution is ently boiled for about one hour with frequent stirring. The undispersed residue is removed by suitable filtration and is washed several times in hot water. The combined washings and filtrate are evaporated to dryness. 75parts of dry productare obtained having a nitrogen content of 8.5% to 8.6%. This material has been found useful for the preparation of artificial fibers.

Example V 1.6 parts of thioglycolic acid and 21 parts of urea are dissolved in water. Sodium hydroxidesolution and water are added as required to obtain parts of solution at about pH 7.0 (:02). 2.5 parts of duck 'feathers are added, and the mixture is heated at about 40 C. about for 18 hours. About 78% of the feather keratin is dis persed by this treatment.

Example VI 1.4 parts of monothioethylene glycol and 24 parts of ammonium thiocyanate are dissolved in water. Sodium hydroxide solution and water are added as required to obtain 35 parts of solution having a pH of about 6.9. 2.5 parts of chicken feathers are treated with this solution for about 18 hours at about 40 During this period about 82% ofthe feather keratin is dispersed.

' Example VII 1.4 parts of monothioethylene glycol and 20.7

' parts of acetamide are dissolved in water. So-

tion and is washed several times in hot water. 40

phates, and 10 parts of dium hydroxide solution and water are added to give 35 parts of solution having a pH of about 7.2. 2.5 parts of chicken feathers are treated with this solution at about 40 C. about for 18 hours. During this period about 59% of the feather. keratin is dispersed.

' Example VIII 1.4 parts of monothioethylene glycol and 27.2 parts of guanidine hydrochloride are dissolved in water. Sodium hydroxide solution and water TABLE I Dispersibilities of keratins in difierent dispersing agents upon'reduction by 0.5 M thioglucol [2.5 g. of keratin was treated for 18 hours at about 40 C. with 35 ml. of solution at pH 7] Guani- NH CNS Form- Acet- Thiourea Synthetic l Kerstin dineHCl amide amide Detergent (8.1 M) M) (10.0 M) (10.0 M) M) 10 Per cent Per cent Per cent Per cent Per cent Per can i Chicken feathers 84 82 66 59 10 79, 80 Duck leather.--" 83 80 41 36 I 6 51, 63 64 b2 l0, 8 44 2s, 30 14 5o 7 e 5 as, 64 61 36 4 6 4 44, 50 36 27 3 6. 4 14, 12 56 2s 2 2 2 4, 3 50 11 o 0 2 2, 1 8 6 4 3 l5 2, 4

l Composed of sodium alkyl sulfates.

- I First values calculated from dry weights seoondvalues calculated from nitrogen analyses.

of residues after acetone extraction;

Tuna III Disperswilities of keratins in M urea upon reduction by diflerent disulphide-splittingagents Many changes and variations the conditions for dispersion shown in the foregoing examples and tables may be made. As a rule, the higher the concentration of protein-dispersing or pro-.

tein-denaturing agent, the greater is the percentage of keratin dispersed, the solubility of the dispersing or denaturing agent being a limiting factor. Agreater degree of dispersion may also be obtained in some cases by increasing th con centration of the disulphide-splitting agent. as for example, for monoethylene thioglycol and thioglycolic acid. An increase in the concentration of NaHBOa, however, often results in a decrease in the extent oi dispersion of the keratin, presumably due to a salting-out eiiect.

Also, it is not necessary in every case that the solution be near the point of neutrality (pH 7.0)

detrimentalinsomecases. IfthepHisincreased above about 111110, dispersion occursii only a disulphide-splitting agent is present; however, the presence of a proteinor proteindenaturing agent, as used in our invention, permits dispersion below p310.

The temperature at which dispersion, according to our invention, is obtained, may range up to about 100 0., and the higher the temperature within this range. the shorter the time required for dispersion, and-in some cases, a higher degree of dispersion is obtained. Therefore, it is recommended that the invention be conducted at a temperature range of up to about 100 C.

Having thus described our invention, we claim: 1. The process comprising heating a keratin material in an essentially neutral aqueous solution containing a sulfur-containing. reductive disulphide-splitting agent and ammonium thiocyanate at' a temperature up to about 100 C. to disperse said keratin material in said solution. I 2. The process comprising heating a keratin material in an essentially neutral aqueous solution containing monoethyleneathioglycol and ammonium thiocyanate at a temperature up to about For example, the dispersibility of human hair in a solution of thioglycol and sodium salicylate is increased as the pH of the solution isincreased about from 6.9 to 11.4. The use or neutral solutions merely minimises the possibility of hydro- C. to disperse said keratin material in said solution.

3. A composition of matterconsistingessen tially of a dispersion of a'keratin material in an essentially neutral aqueous solution containing a sulfur-containing, reductive disulphide-splitting agent and ammonium thiocyanatc.

4. A composition of matter consisting essentially of a dispersion of a keratin materialin an essentially neutral aqueous solution containing monoethylene thioglycol andammonium thiocyanate. I

CHASE B. JONES.

DALI 81 m lytic degradation oi the protein which maybe. 

